Manufacture of spongy-lead plates for secondary batteries.



rrn STATES HERBERT WVILLIAM BUTLER AND JOSEPH HORSNELL MAY, OF LONDONENGLAND, ASSIGNORS TO JOHN IRVING OOURTENAY, OF LONDON ENGLAND.

PATENT OFFICE.

MANUFACTURE OF SPONGY-LEAD PLATES FOR SECONDARY BATTERIES.

SPECIFICATION forming part of Letters Patent No. 715,016, dated December2, 1902.

Application filed January 2, 1901. Serial No. 41,882. ($pecimens.)

To ztZZ whom it may concern;

Be it known that we, HERBERT WILLIAM BUTLER and J osEPH HORSNELLMAY,subjects of the Queen of Great Britain and Ireland, and residents of4 Great Winchester street, in the city of London, England, have inventedcertain new and useful Improvements in the Manufacture of Negative orSpongy Lead Plates or Elements for Secondary Batteries or ElectricalAccumulators, of which the following is a specification.

This invention has for its object to provide for secondary batteries orelectrical accumulators negative pole -plates or spongy-lead elements orplates which have large capacity and which are less liable todeterioration, and consequently have a longer life than such elements orplates as hitherto manufactured.

We employ in the manufacture of negativepole elements or plates amixture of lead oxid (or lead oxids) and powdered carbon (preferablycharcoal) or other suitable organic substance capable of beingdecomposed and oxidized by the action of an electric current, ashereinafter described.

Presuming that charcoal is employed in the mixture,a mixture of ten percent. ,by volume, of powdered charcoal to ninety per cent, by volume, oflead oxid answers well in practice; but we do not limit ourselves tothese proportions. The oxid of lead and carbon are made into a paste byadmixture with a suitable solution, such as either of the solutionscommonly used for mixing the paste or active material of secondarybatteries or electrical accumulators of the pasted or Faure type, andthe paste so made is spread on or applied to the grid or support, whichcan be done in the usual or any suitable way. When the paste so appliedhas sufficiently dried, the element or plate is placed in a formingsolution, which may be one of the usual forming solutions, and anelectrical current is passed through it, it being attached to thepositive pole of the source of electricity, and thereby the carbon orthe equivalent is oxidized and. peroxid of lead is formed, the whole orany desired portion of the carbon or the equivalent being removed by theaction of the said curren t,thus leaving a porous mass of peroxid oflead without any carbon or the like if it has all been oxidized or withsome carbon if it has not all been oxidized. An electrical current isthen passed through the plate or element in the reverse direction tothat in which it was passed as aforesaid, (after changing the solution,if necessary,) and thereby the peroxid of lead is reduced tospongy-lead, and when the peroxid has been so reduced the plate orelement is ready for use in a secondary battery or electricalaccumulator. The solution may be changed at any time before or after thereversal of the current.

The following is an example of the manner in which the invention may beperformed; but we do not limit ourselves to the details of this example:

We make a mixture of powdered charcoal and lead oxid consisting of tenper cent. of charcoal and ninety percent. of lead oxid, (the parts beingby volume,) and we form this into a pasty mass by the addition of asolution of dilute sulfuric acid, and we apply this paste to the grid orconducting-support,which may be done in the ordinary manner. We thenallow the paste to dry, with or Without the application of artificialheat, and We then place the element or plate in a forming solution,which may consist of dilute sulfuric acid only or dilute sulfuric acidcontaining some salt rich in oxygen, such as sodium nitrate, and connectit with the positive pole of a dynamo or other source of electricity, anelement or plate made of plain sheet-lead being connected with thenegative pole of the dynamo or other source of electricity. We pass acurrent of electricity having a density of about one ampere for onehundred square inches of surface of the element or plate through untilthe carbon has been sufficiently oxidized, which is indicated by the gasbeing liberated from the surface of the plate or element, the liberationof the gas being the more violent as the carbon becomes exhausted. Ifsulfuric acid has been used for the forming solution, it is not thennecessary to exchange the solution; but if the forming solution hasconsisted of sulfuric acid mixed with a salt we remove the solution andintroduce another solution formed of dilute sulfuric acid, and we pass asimilar current through, but in the reverse direction, until the mass isreduced to the condition of spongy lead, when the element or plate thustreated is ready for use as the negative pole plates or element in asecondary battery or electrical accumulator.

Although one plate has been mentioned here, in practice, of course,anumber of plates would be treated in a similar manner and formedtogether.

We are aware that it has been before proposed to use carbon in the formof small particles added to the paste which is used in the manufactureof plates or elements for secondary batteries or electricalaccumulators, and this invention does not consist in such addition, butin the subsequent removal (either wholly or partially) of the carbon orequivalent by oxidation by electric action, as hereinbefore described,and then the reduction of the porous mass thus formed to spongy lead byreversal of the electric current.

Having now particularly described and ascertained the nature of the saidinvention and in what manner the same is to be performed, we declarethat what we claim is- 1. The process of producing negative poleplatesor spongy-lead plates or elements for secondary batteries, consisting insubjecting a paste of lead oxid and an organic substance capable ofbeing oxidized by the action of the electric current, applied to a gridor support to the action of the electric current in a forming solutionor solutions the said current being first applied while the element orplate to be formed is attached to the positive pole of the source ofelectricity so as to oxidize the organic substance or any desiredportion thereof and convert the lead oxid into porous peroxid and thenpassing the electric current in a reverse direction to reduce the porousperoxid to spongy lead.

2. The process of producing negative poleplates or spongy-lead plates orelements for secondary batteries, consisting in subjecting a paste oflead oxid and powdered carbon, applied to a grid or support, to theaction of an electric current in a forming solution or solutions, thesaid current being first applied while the element or plate being formedis attached to the positive pole of the source of electricity so as tooxidize the carbon or any desired portion thereof and convert the leadoxid into porous peroxid and then passing the electric current in areverse direction to reduce the porous peroxid to spongy lead..

In testimony whereof we have signed this specification in the presenceof two subscribing witnesses.

HERBERT WILLIAM BUTLER. JOSEPH HORSNELL MAY.

Witnesses:

WILLIAM GERALD REYNOLDS, HENRY DENIS HOSKINS.

